spectrometry (MS/MS) on positive mode (UPLC-APCI-MS/MS). Residual squalene (i.e. non-oxidized) is quantiﬁed on the same run with PDA detection at

205 nm, using pure squalene as standard. Under such conditions, the Limit Of

Detection (LOD) and Limit Of Quantiﬁcation (LOQ) of squalene monohydroperoxides are 10 and 50 ng ml−1, respectively, together with an acceptable reproducibility (coefﬁcient of variation <10 %). LOD and LOQ for residual squalene are